Ábrahám Levente (szerk.): Válogatott tanulmányok VI. - Natura Somogyiensis 19. (Kaposvár, 2010)
BALÁZS A. & ERDŐS L.: Botanical survey of Southern Transdanubian oxbow lakes and the changes of the last 10 years
46 NATURA SOMOGYIENSIS Table 3: The changes in the vegetation of Bresztik between 1999 and 2009 +: the species or association is present in the oxbow lake, -: not present, +: abundant, n.a.: data not available Plant species and associations 1999 2000 2002 2003 2004 2009 Ceratophyllum demersum + + n.a. n.a. n.a. Hydrocharis morsus-ranae + + n.a. n.a. n.a. + Lemrta minor + + + n.a. + Myriophyllum spicatum + Nuphar lutea + + D+ D+ D+ + Nymphaea alba + Nymphoides peltata + + Ranunculus trichophyllus n.a. n.a. n.a. n.a. n.a. + Salvinia natans + + + n.a. + + Spirodela polyrrhiza + + n.a. n.a. n.a. Utricularia vulgaris + + n.a. n.a. n.a. Phragmitetum communis É+, D+ É+, D+ É+, D+ É-,DÉ-.DD+ Thelypteris palustris D+ D+ n+ n.a. D+ Typhetum latifoliae D+ D+ D+ DDSalicetum cinereae É+, D+ É+, D+ É+, D+ É-.D+ ÉD+ Ambrosia artemisiifolia n.a. n.a. n.a. n.a. n.a. + Amorpha fruticosa n.a. n.a. n.a. n.a. n.a. É+ ÉNy+ Echinocystis lobata n.a. n.a. n. a. n.a. n.a. É+ ÉNy+ Solidago gigantea n.a. n.a. n.a. n.a. n.a. + relatively undisturbed. Nymphoides peltata was dominant in the northern part of the oxbow lake in 2000. Since 2000, it has spread in the whole oxbow lake. The disappearance of the water weed species is not due to the Ctenopharyngodon idella according to a local angler, because this fish species has not been introduced to this oxbow lake for years. He said that chemicals had been applied for the eradication of the water-weeds. We found a few individuals of Urtica kioviensis in a section. The invasive Amorpha fruticosa was present in low quantity in the south-western and eastern part of the oxbow lake. These sections are near to the cart-road and contain a lot of stages. Solidago gigantea was considerable only on the eastern shore. Mailáthpusztai-tó: This oxbow lake has the most water-weed species among the six oxbox lakes, although most of them have only low RPM%. Nymphoides peltata has been dominant since 1999. We could find only 1-2 individuals of Nuphar lutea. Nymphaea alba has been present in the most quantity in the northern part of the oxbow lake since 2002 but it can be found along the eastern part of the oxbow lake, too. It was reported in 2004 (CZIROK et al. 2004) that Nymphaea alba was only present in a few quantity in the northern part. However, it was quite abundant in 2009, with scale-values reaching 3-5. Urtica kioviensis has an RPM% value of about 2%. Moreover, it could be found also in the northern part of the oxbow lake in a few sections in low quantities. Also, some other valuable water-weed species were found in Mailáthpusztai-tó, for example Trapa natans, Nuphar lutea , Ranunculus trichophyllus, Myriophyllum spicatum and M verticil latum. There were hardly any invasive species on the shores, we found only a few individuals of Amorpha fruticosa and Solidago gigantea. This oxbow lake is the most appreciative one from a nature conservation perspective as the quantity of the invasive species is very low and the quantity and the number of the protected species are comparatively high. Hótedra: The number of the water-weed species and individuals has changed negatively. Ctenopharyngodon idella may be responsible for this tendency. Nymphaea alba could be found in great numbers in this oxbow lake earlier but we could not find it in
